Added scrool spy (js)

[Grégoire Pineau]

i could be very nice if you could add this js plugin to the doc :
http://twitter.github.com/bootstrap/javascript.html#scrollspy

[Grégoire Pineau]

Here, is the new URL: http://getbootstrap.com/javascript/#scrollspy

[Grégoire Pineau]

ping @mislav

[Mislav Marohnić]

Thanks for the tip; I will think about this when I make updates on the app!

I haven't worked on this for a long while.